Editing Common Text-based Response Protocol

{{Infobox protocol
| name            = Common Text-based Response Protocol
| developer       = [[secondtruthLabs]]
| status          = Stable
| first_published = 2025
| latest_version  = 1.0
| transport       = [[wp:Transmission Control Protocol|TCP]]
| encoding        = [[wp:UTF-8|UTF-8]]
| license         = [[wp:Public domain|Public Domain]]
}}

The '''Common Text-based Response Protocol''' ('''CTRP''') is a foundation protocol for building lightweight, text-based application protocols over [[wp:Transmission Control Protocol|TCP]]. Developed by [[secondtruthLabs]], it defines common conventions for simple request-response communication patterns.

== Overview ==

CTRP serves as a base layer upon which application-specific protocols can be built. Rather than defining a complete application protocol itself, CTRP establishes conventions for message formatting, status codes, and connection handling that derived protocols inherit and extend.

=== Design philosophy ===

CTRP follows a minimalist approach inspired by classic internet protocols like [[wp:Finger protocol|Finger]] and [[wp:Gopher (protocol)|Gopher]]. Key principles include:

* Simple enough to implement in a weekend
* Consistent patterns across derived protocols
* Optimized for text content delivery
* Minimal overhead

== Technical specification ==

=== Request format ===

Requests consist of a single line terminated by [[wp:CRLF|CRLF]] (<code>\r\n</code>):

{{Code example
| language = text
| caption  = Basic request format
| code     = COMMAND [arguments]\r\n
}}

The maximum request line length is 1024 bytes.

=== Response format ===

Responses begin with a status line, followed by optional content:

{{Code example
| language = text
| caption  = Response format
| code     = <status_code> <status_message>\r\n
[content lines]\r\n
.\r\n
}}

Content is terminated by a line containing only a period (<code>.</code>).

=== Status codes ===

CTRP uses a hierarchical status code system:

{| class="wikitable"
|-
! Range !! Category !! Description
|-
| 1x || Informational || Request received, continuing process
|-
| 2x || Success || Request successfully processed
|-
| 3x || Redirection || Further action needed
|-
| 4x || Client Error || Request contains bad syntax or cannot be fulfilled
|-
| 5x || Server Error || Server failed to fulfill valid request
|-
| 6x || Service Error || Service-level issues
|}

Common status codes:

{| class="wikitable"
|-
! Code !! Message !! Meaning
|-
| 20 || OK || Success
|-
| 21 || OK+MORE || Success, more content available
|-
| 40 || BAD REQUEST || Malformed request
|-
| 41 || NOT FOUND || Requested resource not found
|-
| 42 || FORBIDDEN || Access denied
|-
| 50 || ERROR || General server error
|-
| 51 || NOT IMPLEMENTED || Command not supported
|}

=== Encoding ===

All CTRP communication uses UTF-8 encoding with CRLF line endings. This ensures consistent handling across platforms while supporting international character sets.

=== Transport security ===

CTRP supports optional [[wp:Transport Layer Security|TLS]] encryption. Implementations typically offer both plain TCP and TLS-secured connections on separate ports.

== Derived protocols ==

The following protocols are built on CTRP:

* [[AgentFinger]] – AI agent discovery and information

== See also ==

* [[AgentFinger]]
* [[Trivial Service Discovery Protocol]]
* [[wp:Finger protocol]]
* [[wp:Gopher (protocol)]]

== References ==

{{Reflist}}

== External links ==

* [https://github.com/secondtruth/ctrp CTRP Specification Repository]

[[Category:Communication Protocols]]
[[Category:Request-Response Protocols]]
[[Category:Foundation Protocols]]
{{stLabs protocol}}